1. Field of the Invention
The present invention relates to an image forming apparatus applied to any of a copier, a printer, a facsimile, or a MFP composed of these machines, all of which transfer a toner image onto paper through a xerographic technique, and more specifically to a tandem-type image forming apparatus that transfers a color image by use of an intermediate transfer unit.
2. Description of Related Art
A tandem type color image forming apparatus is structured to have a plurality of photosensitive drums arranged along a moving direction of an intermediate transfer belt, and transfers onto the intermediate transfer belt toner images of respective colors formed on the photosensitive drums and then transfers them from the intermediate transfer belt onto paper. In this image forming apparatus, (for the transfer of the toner images on the photosensitive drums onto the intermediate transfer belt), primary transfer rollers press the intermediate transfer belt against the photosensitive drums. Moreover, the tandem type color image forming apparatus is provided in: a mode of a photosensitive unit having the photosensitive drum assembled with a charging device that charges a surface of the photosensitive drum; and a mode of an intermediate transfer unit having the intermediate transfer belt stretched over a driving roller, a driven roller, and a primary transfer roller, and therefore upon replacement of the photosensitive drum or the intermediate transfer belt, the replacement is done on an individual unit basis.
In the unit replacement, it is preferable that directions in which the photosensitive unit and the intermediate transfer unit are drawn out be different from each other since it decreases aperture parts of the apparatus main body to increase rigidity and also improve image quality. Therefore, provided is a structure such that the photosensitive unit can be drawn out along an axial direction of the photosensitive drum and the intermediate transfer unit can be drawn out along a moving direction of the intermediate transfer belt.
Upon the replacement of the photosensitive unit and the intermediate transfer unit described above, for the purpose of avoiding scratch of the photosensitive drum and the intermediate transfer belt, the pressing against the photosensitive drum side by the primary transfer roller needs to be released. Thus, conventionally known is an image forming apparatus which vertically moves, in conjunction with opening and closing of a front door, an entire intermediate transfer unit including an intermediate transfer belt and a primary transfer roller, which vertically moves and tilts a right side of the intermediate transfer unit in conjunction with opening and closing of a right side door, and which vertically moves and tilts a left side of the intermediate transfer unit in conjunction with opening and closing of a left side door.
However, the conventional image forming apparatus requires: a conversion mechanism that converts opening and closing operation into operation of vertically moving and tilting the entire intermediate transfer unit; and a driving mechanism that vertically moves and tilts the entire intermediate transfer unit. Thus, an extensive and complicated structure results, bringing about a problem that assembly is a hard task.